Swingable axle stabilizer system for paralleling natural steering forces



A. C. STOVER SWINGABLE AXLE STABILIZER SYSTEM FOR PARALLELING NATURAL STEERING FORCES June 30, 1953 2 Sheets-Sheet 1 Filed 001". 5, 1949 June 30, 1953 t A, C, STOVER 2,643,895

SWINGABLE AXLE STABILIZER SYSTEM FOR PARALLELING NATURAL STEERING FORCES Filed Oct. 3, 1949 2 Sheets-Sheet 2 l' I /l 49 Ii l Je 43 l. /f ya/f I J3 f3 INVENTOR.

ANC/.4 C1670 VIA? L Toma/VMM Patented June 30, 1953 UNITED STATES iiATENT OFFICE SVVINGABLE AXLE STABILIZER SYSTEM FOR PARALLELING NATURAL STEER- ING FORCES A@upplirration October 3, 1949, Serial No. 119,222

2 Claims.

This invention relates to vehicles of the type having tandemly arranged axles supported `for turning movement independently of one another about vertical axes,

In vehicles of the above general type, two or incre of the axles are pivotally supported on the frame so that when the vehicle is turned from a straight course of travel by manipulation of the front steering wheels the pivoted axles will turn in the appropriate directions to enable the wheels on the pivoted axles to turn with the front steering wheels. This action has the advantage of minimizing side and lateral skidding of the ground engaging wheels when the vehicle is turned in one direction or the other but also has the disadvantage of decreasing the stability of the vehicle. With the above in view, it is an object of this invention to provide a stabilizer system the function of which parallels the 'action of the steering forces that cause the pivoted axles to track with the front steering wheels. In this manner, the stabilizer system does not interfere with the natural tracking pattern assumed -by the pivoted axles when a turn is negotiated, and at the same time it cancels out other forces tending to disturb the natural tracking pattern.

In accordance with this invention, a pair of axles are spaced apart longitudinally of the frame on opposite sides of, and equal distances from, the vertical axial center of suspension. Because of this arrangement, the axles in responding to their natural tracking functions will be caused to assume equal, opposite angles with respect to the longitudinal axis of the vehicle.

It is another object of this invention to connect one end of one pivoted axle tothe corresponding end of a second pivoted axle with a closed hydraulic system having displacement means and to connect the other end of the rst axle to the corresponding end of the second axle with a second closed hydraulic system also embodying displacement means.

In 'accordance with this invention, each displacement system comprises two cylinders having pistons slidably supported therein and respectively connected to corresponding ends of iirst and lsecond axles in a manner such that turning movement of the axles displaces hy draulic fluid in the systems to maintain turning movement of the axles in opposite directions throughout vsubstantially the same dis tance of angular travel. Accordingly the function of the hydraulic stabilizer system parallels the action of the natural steering forces and,

therefore, does not interfere with the natural tracking pattern assumed by the pivoted axles.

One of the deflecting forces tending to disturb the natural steering pattern assumed by the pivoted 'axles is centrifugal force. This results from the vconstantly changing direction of forward movement of the vehicle and tends to cause the axles to turn in the same 4direction in their relation to the longitudinal centerline of the vehicle. The effect of centrifugal force is cancelled out by the hydraulic iluid system of this invention which prevents turning movement of the axles in the same direction.

In addition to centrifugal force, other conditions such as when uneven rolling resistance is met lby either wheel of an axle, have a tendency to cause an axle to oscillate in opposition to the natural steering force. The functioning of the hydraulic fluid stabilizer is to combine the forces represented by the natural steering functions of two axles making available suiicient force to maintain directional stability, as these conditions are met by the indivi-dual axles.

It is a further object of this invention to prof vide selectively operable means for preventing fluid flow through the systems to thereby lock the axles against turning movement in either direction. f

The foregoing as well as other objects will `be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure l is a fragmentary plan viewof a tandem axle vehicle embodying the features of vthis invention;

Figure 2 is a side elevational view of the conn struction shown in Figure 1;

Figure 3 'is a diagrammatic plan view showing the hydraulic fluid displacement systems between the turning wheels of the vehicle;

Figure 4 is a `cross-sectional View taken on the line 4 4 of Figure 1;

Figure 5 is a sectional view taken on the line 5--5 of Figure 4,

Figure 6 is a fragmentary side elevational View showing the manner in which the suspension springs are mounted,

Figure 7 is a sectional view taken on the line l-l' of Figure l; and

Figure 8 is a diagrammatic sectional view of a typical shut-off valve which may be employed in the hydraulic displacement systems.

In Figure 1 of the drawings, I have shown a vehicle chassis having a frame It comprising side sills Il secured in laterally spaced relation-v ship by crossbars I2. Extending beneath the frame I in a direction transverse to the length of the frame is a plurality of axles designated by the numerals i3, I4 and I5. Each axle is con nected to the frame l!! by a pair of' semi-elliptical leaf springs It respectively supported at opposite sides of the frame for movement relative to the frame in the direction of length of the latter. As shown in Figure 6 of the drawings, the adjacent ends oi the springs I6 at opposite sides oi the frame IIJ are connected together by chains Il and sprockets I8. The sprockets. i8 are supported for rotation on the frame below the ad= jacent ends of the springs and the chains I1 are respectively reeved over the undersides of the sprockets I8. The upper ends of the chains are respectively pivotally connected to.. the adjacent ends of the springs by suitable shackles i9 in a manner such that all of the springs cooperate. to control movement of the chassis frame i relative to the axles` The springs i at opposite ends oi the frame have the. extremities thereof slidably supported on seats 2B which in turn are secured to the frame It. Thus all of the springs are capable of limited shifting movement longitudinally of the frame- I. The pairs oi leaf springs is at opposite sides o the frame Io are respectively connected intermediate the ends thereof to the axles by any suitable type oi clamping means which forms` no part of the present invention and need not be described in detail.

In the present instance, the axle I3 is a driving axle and is operatively connected to the power source or internal combustion engine (not shown) by a suitable propeller shaft 2i. The axle I5 is also shown herein as a driving axle and is connected to the power source or internal combustion engine (not shown) by a propeller shaft 22. The intermediate axle I6 is preferably an idler axle and merely cooperates with the other axles in supporting the load.

'I'he axles i3, I4 and I5 are respectively con= nected to the chassis frame I for movement relative to the chassis frame independently of one another, The connection between the intermediate axle I and the frame I0 comprises a mounting 23. The mounting 23 comprises concentric rings 24 and 2d. The outer ring 24 is supported for swinging movement about a horizontal axis extending substantially parallel to the axis of the axle I4 and is positioned intermediate the side sills I I of the frame (I3. The inner ring 24' is supported by the outer ring 24 for rotation about the axis of the outer ring 2e. The mounting 23 is shown in my copending application Serial No. 119,223, filed October 3, 1949, and is not described in detail herein. lit will suice to point out that the ring 24 has a pair of trunnions 25 suitably secured to diametrically opposite sides thereof and journaled in suitable bearing blocks 26. The bearing blocks 26 are suitably secured to a cross member of the frame Io in positions to enable free rocking movement o the ring 24 about a horizontal axis extending substantially parallel to the axle I li. As shown in Figures 1 and 7 of the drawings, op posite end portions of the axle Ill are respectively connected to diametrically opposite sides of the ring 2li' by struts 35. Thus the axle il may move angularly about the axis of the ring 25 and may also move in an up and down direction relative to the frame II).

The axles I3 and I5, in addition to being connected to the chassis frame I0 for swinging and angular movement, are also capable of turning movement so as to turn with the front steering wheels (not shown) of the vehicle. The axle I3 is connected to the frame I El by a mount ing s@ and the axle I5 is. connected to the frame iii bya mounting 4I. These two mountings are identical in construction and accordingly a description of one will suiiice for both. With this in View, reference is made more in detail to Figures 41 and 5 of the drawings wherein the mounting lil is shown in detail. This mounting comprises a double trunnion having an outer ring l2 and an inner ring 43. Two vertically aligned trunnions 46 are respectively secured to the top and bottom of the outer ring 42. The top trunw nien d is journaled in a bearing l5 secured to a tubular crossbrace 45 intermediate the ends thereoi,` The bottom trunnion ill is journaled in a bearing 4l which is secured to a second tubular brace at.. intermediate the ends of the latter. The tubular brace 46 extends between the side sills il of the frame. IB. and is welded or otherwise permanently secured to the sills. The bottom tubular brace 4 8 extends between the lower ends of a pair of plates 55 having the upperends respectively welded tor the side sills II. Suitable vertically extending gusset plates 59 extend between the tubes 55 and 48 at opposite ends of the latter. These plates are respectively welded to the depending plates 4,9 and are also welded to the tubes d5 and (i3 in order to provide a rigid support for the mounting 4I. The above conswruction is such that the mounting il! is sup ported in a position to enable the propeller shaft 22 to be extended through the inner ring t3 of the mounting. The mounting le is supported in a similar manner on the chassis frame lil in a position to enable free passage of the propeller shaft 2l through the inner ring.

Two trunnions 5I are secured to diametrically opposite sides of the. inner ring s3 with their axes in alignment and extending parallel to the axis of the axle I5. The trunnions 5I are respectively journaled in bearings 52 secured to the outer ring 42 in a manner to permit swinging movement of the inner ring i3 relative tothe outer ring 42 about a substantially horizontal axis which is parallel to the axis of the axle I5. It will further be noted from Figure 5 of the drawings that the ring d3 rotatably supports a ring section 5.3' in a manner such. that the ring section may rotate freely about the axis of the ring s3.

The ring section fla is connected at diametri.- cally opposite sides to the axle I5 by a pair of struts 53 which may be similar in construction to the struts 35 previously described. In any case, the construction is such as to permit the axle I5 to turn about the vertical axis of the trunnions 44, to swing about the horizontal axis of the trunnions 5 I, and to move angularly about the axis of the ring 43, Since the mounting il is identical to the mounting i I, it follows that the axle I3 may move in a manner similar to the axle I5.

Since both the axles I3 and I5 are capable of turning movement about substantially vertically extending axes, it follows that the leaf springs IG connecting these axles to the frame are subjected to lateral stresses during turning movement of the axles. In order to materially reduce these stresses, it is preferred to connect the leaf springs to the axles in a manner to enable limited rocking movement of the axles relative to the springs about the axes which extendgenerally parallel to the axes of turning movement of the axles. It will also be understood that the chains yIl and seats 2Q allow lateral shifting movement of the springs It relative to the frame during rocking movement of the axles. A spring mounting capable of accomplishing the above result shown generally in Figure 6 of the drawings and is designated by the numeral This spring mounting forms the subject matter of my copending application Serial No. 119,224, led October 3, 1949, now Patent Number 2,624,593, and is therefore not described in detail herein. Due to the nature oi the mountings le and di and owing to the irictional engagement of the ground engaging wheels on these axles with the road surface, it follows that both axles I3 and le will turn with the front steering wheels of the vehicle. it will be noted that the axles I3, E61 and I5 are spaced apart equal distances lengthwise of the frame so that axle le is at the center of suspension or support. Thus, axles i3 and l5 are on opposite sides o1?, and equidistant from, the center of suspension (Figure 2). This construction, taken in connection with the fact that the axes about which axles 53 and i5 turn are spaced from the respective axles to enable tracking with the front steering wheels (not shown), assures that the axles I3 and i5 will track, by turning an equal amount in opposite directions when the vehicle is turned from a straight course. (Figure 3). Any delecting forces tending to disturb the natural tracking pattern oi' axlesis and I5 are countered by the hydraulic stabilizer tem (described below), the function oi which is to parallel the action of the steering forces which establish the natural tracking pattern. Y

With the above in view, reference is again made to Figure 1 of the drawings wherein it will be noted that opposite ends of the axles is i5 are in effect respectively connected by two closed hydraulic systems designated generally by the numerals Eiii and SI. As shown in Figure the drawings, the system Sti comprises a pair of cylinders 62 and 63 respectively supported on one side sill i l of the frame adjacent the mountings i and di. A piston 52' is slidably supported in the cylinder G2 and is operatively connected to one side of the outer ring i2 of the mounting fill by an arm eil. A piston 63 slidably supported in the cylinder $33 andis connected to the corresponding side of the ring l2 of the mounting il by an arm t5. The end of the cylinder S2 at the rear side of the piston 52 has a fluid connection eil with the cylinder 63 at the rear side of the piston in this cylinder and the front end of the cylinder 62 is connected by a conduit 55 to the front end of the cylinder 53. The fluid system 5I at the opposite side of the vehicle also has two cylinders and 53 respectively supported on the adjacent side sill i l. The rear end of the cylinder El is connected to the corresponding end of the cylinder 63 by a conduit SS and the front end of the cylinder El is connectecl to the front end of the cylinder GS by a conduit lil. The piston El in the cylinder el is connected to the side of the ring 42 of the mounting it opposite the side to which the piston S2 is connected and this is accomplished by an arm l2. The piston til in the cylinder is connected to the corresponding side of the ring i2 associated with the mounting il by an arm it which is opposed to the arm S5. Both systems include reservoirs 'il and are completely filled with a suitable hydraulic fluid medium.

It follows from the foregoing that when the axle I3 is turned about the vertically aligned axes of the trunnions lill in an anti-clockwise direction as viewed in Figure 1 of the drawings, the pistons S2' and El' in the respective cylinders 32 and 6l are moved in opposite directions, by the ring l2 of the mounting fili for the axle i5. More particularly, the piston 52' moves forwardly in the cylinder c2 and the piston lil moves rearwardly in the cylinder El. The displacement of hydraulic:v fluid medium in the two systems et and El, resulting from the above movement of the pistons E2' and el', creates a thrust tending to cause the piston t3 in the cylinder to move rearwardly and the piston 63' in the cylinder 68 to move forwardly. Since the pistons S3 and t3 are respectively connected to opposite sides of the ring e2 associated with the mounting il Y and since this ring LlZ'is connected to the axle I5, it follows that the thrust created by pistons 62 and 6l tends to turn the latter axle in acloclrwise direction or in a direction opposite the direction of turning movement of the axle ifi and in an amount equal to that of axle I3. the effect of the hydraulic systems is to parallel the natural tracking pattern established by the steering forces when a turn is made. Moreover, any tendency for the axles to be deflected from the natural steering pattern is resisted and the stability of the vehicle is greatly improved.

Under some conditions, it may be advantageous to lock the axles I 3 and l5 against turning movement with the front steering wheels and this may be accomplished by providing a shut-off valve 'I3 in the two hydraulic systems ci? and 5I. This valve is normally open so that both hydraulic systems are operative and may be closed by manipulating an air valve lfi through a suitable control (not shown) located within the cab of the vehicle.

Figure 8 illustrates diagrammatically a typical shut-off valve which may be employed for the above purpose. This valve is shown by way of example only, since any suitable shut-off valve may be employed. Valve 'I3 comprises a cylindrical body It having pistons lli slidably supported therein. Conduits iis and l@ communicate with the body adjacent one end thereof and conduits 50 and S6 communicate with the body adjacent the other end. The conduits 59 and l!) and the conduits S0" and @d normally communicate through the valve body, the pistons l being urged into engagement with each other at the center of the valve body by springs l. vWhen it is desired to lock the axles I3 and I5 against turning movement, air Vvalve lll is manipulated to admit air from a source not shown into valve body 'i3' through conduit 13" between the pistons, thus urging the latter apart against the action of the respective springs and into blocking relation to the conduits $9 and lt and the conduits im and 6E.

From the foregoing, it will be noted that the systems 60 and Si actually provide'a hydraulic balance between the axles I3 and i5, and assure turning of these axles in opposite directions throughout substantially the same distance of angular travel, notwithstanding lateral thrusts applied to either axle through the ground engaging wheels in the axles. Also, the two hydraulic systems Gli and 6I, connecting corresponding ends of the axles I3 and I5, enable one axle to resist any dedecting forces applied to the other axle so that both axles cooperate to promote stability of the vehicle.

What I claim as my invention is:

1. A vehicle having in combination a frame, means for supporting the frame including a pair Thus ce t of axles extending in a directirm` transverse to the frame and spaced from each other lengthwise of the frame, means respectively pivotally supporting the axles on the frame for turningf movement relative tothe frame about substantially vertically extending axes, said axes being spaced from the respective axles lengthwise of the frame to enable said axles to turn in appropriate directions and conform to a natural steering pattern established upon turning of the frame from a straight course of travel, the center of support established by said means for supporting the frame being midway between said axles, whereby said axles turn in opposite directions throughout substantially the same angular extent in conforming to a natural steering pattern, and a pair of closed hydraulic displacement systems respectively interconnecting corresponding ends of the axles so that turning movement of one axle in one direction imparts a turning movement to the other axle in the opposite direction throughout substantially the same angular distance of travel, said systems being free from communication with each other and each having a pair of cylinders supported on the frame and having pistons respectively slidably supported in the cylinders, fluid conduits respectively connecting the cylinders of each system at opposite sides of the pistons, whereby sliding movement of one piston in its cylinder imparts a sliding movement to the other piston of the same system by the displacement of hydraulic fluid, and connections between the pistons of each system and the respective axles responsive to displacement of hydraulic fluid in said systems to cause a turning movement of the axles about their respective vertical axes in opposite directions and throughout substantially the same angular distance of travel.

2. A vehicle having in combination a frame, means for supporting the frame including a pair of axles extending in a direction transverse to the frame and spaced from each other lengthwise of the frame, means respectively pivotally supporting the axles on the frame for turning movement relative to the frame about substan- 4 tially vertically extending axes, said axes being spaced from the respective axles lengthwise of the trarne to. enablesaid. axles te turn in appro-f priate. directions and conform t0 a natural steering pattern established upon turning of the frame from a straight course of travel, the center 0f Support established by said means for supporting the frame being midway between said axles, wherebyv said axles turn in opposite directions throughout substantially the same angularextent in conforming to a natural steering pattern, and a closed hydraulic displacement system interconnecting said axles so that turning movement of one axle in one direction imparts a turn"y ing movement to the other axle in the opposite direction throughout substantially the same an- Y gular distance or travel, said` system having a pair of cylinders supported on the frame and having pistons respectively slidably supported in the cylinders, fluid conduits respectively connecting the cylinders at opposite sides of the pistons, whereby sliding movement of one piston in its cylinder imparts a sliding movement to the other piston by the displacement of hydraulic fluid, and connections between the pistons of each cylinder and the respective axles responsive to displacement of hydraulic iluid to cause a turning movement of the axles about their respective vertical axes in opposite directions and throughout substantially the same angular distance of travel.

' ANCIL C. STOVER.

References Cited in. the file 0f this Dlnt UNITED STATES PATENTS 

